Apparatus and method for providing a power line communication device for safe transmission of high-frequency, high-bandwidth signals over existing power distribution lines

ABSTRACT

The fiber optic isolator of the present invention transports data signals between high voltage power lines and a communications interface device, bypassing a step down transformer to low voltage power. The communication interface device includes a low voltage power line as well as telecommunications and wireless interfaces. The signals are coupled and de-coupled off of a high voltage power line by a power line coupler. The fiber optic isolator gets the signals (in light form) and transports them to and from the communications interface device. This insulates the system from current flow between the high voltage power lines and the communications interface.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. §119(e) fromprovisional application No. 60/268,519, filed Feb. 14, 2001. The60/268,519 provisional application is incorporated by reference herein,in its entirety, for all purposes.

FIELD OF THE INVENTION

[0002] The present invention is drawn to a power line communicationssystem for transmitting and receiving high frequency, high bandwidthsignals safely over power lines. The system comprises a power linecoupler, a fiber optic isolator and a communications interface tovarious media. The present invention is related to a portion of thesystem concerned with the fiber optic isolator and communicationsinterface.

BACKGROUND

[0003] With well-established power distribution systems (PDSs) alreadyin place throughout much of the world, an efficient power linecommunication system (PLCS) could provide more users with high-speedtelecommunications access with the minimum investment of “add-on”devices.

[0004] The infrastructure for providing broadband Internet access ispresently insufficient to meet demand. A power distribution system(PDS), however, could be an ideal vehicle for carrying communicationssignals in order to meet this demand. Development of a power linecommunication system (PLCS) would therefore provide more users withhigh-speed telecommunications access. Since the PDS is already built,the time required to implement a PLCS would be minimal.

[0005] Of course, there are a series of problems to be overcome before aPDS can be used as an efficient, high-speed power line communicationsmedium. The following issues, while not exhaustive, are representativeconsiderations of what such a system would require in order to use anexisting PDS to transport communication data: a sufficient signal tonoise ratio, non-disruptive installation of the “add on” device; safetymeans such that users and circuitry are protected and isolated fromstray current; a signal carrier with a frequency sufficient to supporthigh data transfer rate (e.g. 10 Mbps); means for the data signal tobypass a distribution transformer without loss; bidirectional datatransmission; coupling devices that do not interfere with data signalhandling; an independent power source for electronic conditioningcircuitry at power line interfaces; a power line interface that isimpervious to extreme environmental conditions; and means for the datato be readily routed to intended locations without loss.

[0006] Given the advantages of being able to use the existing PDS forhigh-speed data communication, an effective method is required to coupleand decouple the signals onto and off of a high or medium voltage powerline. The coupling and decoupling of the data signal must be at a levelsufficient to maintain an adequate signal to noise ratio in order todiscern between the data signal and noise or interference on the line.For any method developed, a significant challenge lies in being able tomitigate the adverse effects of the high voltage 50-60 Hz power signalmight have on the communications signal. Additionally, safety from highvoltage is of concern.

[0007] Whyte, et al. in U.S. Pat. No. 4,142,178 observe: “The use of thedistribution network conductors for the transmission of carriercommunication signals presents many problems not encountered in highvoltage transmission line communication systems. Some of these problemsinclude the poor high frequency impedance characteristics and the highlevel of electrical noise present on the distribution network conductorswhich, along with the plurality of distribution transformers and powerfactor correction capacitors attached to the distribution network,rapidly attenuate the communication signals.”

[0008] Whyte teaches using a direct circuitry from a line coupler to aremote data terminal thus bypassing the PDS transformer, which is theprimary source of data attenuation. The main use for the transmission ofcommunication signals addressed by Whyte was to perform distributionfunctions such as automatic reading of utility meters and selective loadcontrol. Those functions are still desirable, but the function of highspeed, high bandwidth communication transmission preclude directconnection from a transformer to remote data terminals economically.

[0009] Use of a low voltage power distribution system as a datacommunications carrier within a premise is well known. Abraham, U.S.Pat. No. 6,014,386 teaches a communications network within a buildingusing the AC wiring as the infrastructure of the network. Differenttypes of appliances using digital signals may be included within thenetwork. The Abraham patent uses an impedance matching scheme to directa specific signal to a specific location. Couplers at a control locationhave unique impedances that are matched by corresponding couplerselsewhere within the building. Thus, specific signals will be de-coupledbased an impedance match. Abraham also teaches the use of dielectricinductors in circuit with capacitors to tune the impedancecharacteristics of couplers.

[0010] In a similar manner, Abraham in U.S. Pat. No. 5,625,863 teachesthe distribution of multiple video signals distributed within a buildingusing the building's AC wiring as the distribution system. Uniqueimpedance settings direct the signals to unique locations. Abraham inU.S. Pat. No. 5,818,127 describes a distribution system for FM signalswithin a building by use of the building's AC wiring.

[0011] Abraham in U.S. Pat. No. 5,717,685 describes the coupling of datasignal on and off a building's AC wiring infrastructure. His inventionuses capacitive circuits in serial connection. The circuitry alsoincludes air-core transformers. This arrangement allows impedance tuningof the specific couplers. While Abraham claims a system with a fiberoptic source for an input signal in his U.S. Pat. No. 6,014,386 patent,there is no description as to the use of fiber optic isolators.

[0012] Abraham also states that the utility firm may use thecommunications system to communicate utility meter information over thePDS.

[0013] Methods for avoidance of distribution transformers are wellknown. Perkins in a series of patents including U.S. Pat. No. 4,473,816teaches a communications signal bypassing a multi-phase powertransformer where the signal uses the PDS as a carrier. The signal isbidirectional and uses conductive material to affect the bypass. Theinvention uses multiple capacitors in parallel to neutralize thecoupling impedance. Further, the winding ratio, R, between the primaryand secondary windings ratio is maintained in the signal frequencyacross the signal bypass. Signal carrier frequency is in the 3-10 KHzrange. Similarly, Perkins in U.S. Pat. No. 4,473,817 teaches acommunications signal bypassing a single-phase power transformer.

[0014] Kennon, U.S. Pat. No. 4,644,321 uses a non-intrusive coupler tocapture the data signal. Kennon teaches the use of a toroid having amultiplicity of turns of a conductor that is in circuit with anamplifier and receiver. The toroid core is non-conductive. The signalthus inductively de-coupled is amplified and used for a load managementand filed configuration utility terminal. The system requires a batteryfor circuitry management.

[0015] Brown, U.S. Pat. No. 5,949,327 teaches the use of transformerbypass by coupling using capacitors connected to the primary andsecondary terminals of the step transformer. Brown recognizes the needfor multiple couplings at different points within the EDN (ElectricalDistribution Network or, as referred to in the present description asPDS). Brown also teaches that the communication system use a highfrequency signal carrier technique such as CDMA.

[0016] Moore, U.S. Pat. No. 5,210,519, describes a communication systemthat couples data signal from a transmission source using an inductorand de-couples the data at the receiver. This methodology is applied ina closed network and requires selective de-coupling as opposed torouting of the signal. Further, Moore teaches the use of a secondtransformer for reversing any inductor core saturation that may haveoccurred in the data de-coupling. This method requires time division ofthe data coupler between data coupling and saturation neutralization.

[0017] Dzung, European Pat. Application EP948143, describes a highvoltage power line communication system that combines multiple sourcedata signals, couples the combined signal onto multiple power linesusing capacitive coupling and de-couples and demodulates the signals,separating and converting the signals back to the original form at thereceiver.

[0018] Power lines can be located in areas with extreme environmentalconditions.

[0019] Thus, the mechanical design must ensure proper operation whenexposed to these extreme conditions and also maintain the required levelof safety. Furthermore, any methods developed should be designed so asto have minimal impact to service of customers during installation.

[0020] As stated above, public safety is an absolute requirement. Anysystem using the PDS must isolate the end user (and public in general)from exposure to electric current. The PDS steps medium and high voltagepower down to low voltage power (approximately in the 100-240 voltrange) using transformers. Transformers are designed to filter out andground high frequency signals as a safety precaution. Since a highfrequency signal carrier is the ideal medium for high bandwidth datatransfer, a communications data delivery system needs to circumvent thetransformer filtration process while preserving safety protection.

SUMMARY OF THE INVENTION

[0021] It is an object of the present invention to provide a safeinterface to a power line coupler for use with a power linecommunication system (PLCS).

[0022] It is still another object of the present invention to provide abypass between a high voltage power line coupler and across a powerdistribution transformer.

[0023] It is a further object of the present invention to provide abypass across a power distribution transformer wherein the data signalis preserved and consistent on either side of each of the transformer.

[0024] It is yet another object of the present invention to provideelectrical current isolation between components and circuits within thePLCS by use of dielectric materials between components of the PLCS.

[0025] It is another object of the present invention to provide a highspeed power line communication system (PLCS) using inductive signalcoupling where the coupler's core stay's unsaturated.

[0026] It is yet another object of the present invention to provide aPLCS that performs data packet management.

[0027] It is a further object of the present invention to provide apower line coupler for use with a PLCS that is non-intrusive.

[0028] It is still a further object of the present invention to providea power line coupler for use with a PLCS that inductively drawsoperating power from the power line.

[0029] It is a further object of the present invention to provide apower line coupler device for use with a PLCS that is self-contained andis nearly impervious to environmental conditions.

[0030] It is another object of the present invention to provide a PLCSthat uses a toroid inductor to inductively couple and de-couple signalsto and from a power line.

[0031] It is yet another object of the present invention to provide apower line coupler that provides an electro-optical transducer tointerface with a fiber optic insulator.

[0032] It is still another object of the present invention to provide anon-intrusive power line coupler that is hinged for ease ofinstallation.

[0033] It is still a further object of the present invention to providea quality monitoring feedback system whereby a power company.

[0034] The PDS topology can be used to deliver high-speed communicationsto residential homes in a cost effective way. Applications for suchcommunication systems include high speed Internet, telephony, videoconferencing and video delivery. This recitation of applications is notmeant to be exhaustive.

[0035] The system involves coupling and de-coupling communications databetween a data source and a PDS. High frequency signals allow highbandwidth transfers (the higher the frequency of the data carrier, themore cycles per unit time available for data transfer). The carriershould exhibit high signal to noise characteristics relative to theunderlying system of a 50 or 60 Hz PDS. (The U.S. standard is 60 Hz, butmost countries use a 50 cycle per second power system.)

[0036] The data signals are coupled on to and off of the power line witha power line coupler (PLC). One embodiment of the present invention usesan inductive method to couple and de-couple data signals off of thepower line. A toroid with conductive windings is placed around the powerline. This method effectively provides a transformer between the powerline and the PLC thus facilitating the transmission and receiving of thedata signal. For the PLC side of the transformer, the number of windingsand the orientation of the windings around the magnetic toroid is guidedby the desire to maximize the flux linkage.

[0037] The type of signal used on this channel can be almost any signalused in communications (CDMA, TDMA, FDM, OFDM to name a few). A widebandsignal such as CDMA that is relatively flat in the spectral domain ispreferred to minimize radiated interference to other systems whiledelivering high data rates.

[0038] Since communications signals are very high frequency, a step downtransformer would filter a signal coupled on the power line. The presentinvention avoids this by bypassing the transformer with a power linebridge (PLB). The PLB de-couples data signals from the medium or highvoltage line a short distance from a transformer. The PLB interfacesbetween the power line on the primary of the transformer and the LV lineon the secondary of the transformer. (The primary is the side of thetransformer where the relatively high voltage enters; the secondary isthe side of the transformer where the stepped down, lower voltage exitsthe transformer.)

[0039] The PLB is used to prevent the relatively high voltage frompassing to the transformer's secondary side yet allowing thecommunications signal to pass between the PDS on either side of thetransformer by using an isolator. A preferred embodiment of the presentinvention is to use an optical medium. The de-coupled signal from therelatively high voltage power line is converted to light energy (i.e.light signal) by using a transducer and transmitting the light signalover a nonelectric conductive but light conductive medium. In a likemanner, light signals from the light conductive medium are converted toelectrical signals for coupling to the power line.

[0040] One embodiment of the present invention uses a fiber optic cableas the isolator. The isolator is a light pipe that bypasses thetransformer. Fiber optic cable is a dielectric thus insulating the PDSon the secondary transformer side from relatively high voltage.

[0041] The signal is next modulated and de-modulated by a first modem.The signal goes through a data router and then a second modem. Therouter serves the purpose of matching data packets with specificmessages and destinations. The second modem modulates and de-modulatesthe signal in a form consistent with transport over a LV power line.

[0042] The light signal is converted back to an electronic signal andthen coupled onto the LV power line (LV coupler). In an embodiment ofthe present invention a second isolator is inserted in the systembetween the second modem and the data router for conversion of the lightsignal to electrical signal. Additionally the isolator proves anadditional layer of safety because of the dielectric quality of thesecond isolator.

[0043] The high speed, high frequency signal is then delivered, over theLV power line to the end user's residence or place of business. A powerline interface device (PLID) serves as the gateway between the enduser's various data appliances and local area network (LAN) and the highspeed data transport.

BRIEF DESCRIPTION OF DRAWINGS

[0044]FIG. 1 discloses the typical electric distribution topology of theprior art.

[0045]FIG. 2 illustrates typical electric distribution topology modifiedfor communication in accordance with the present invention.

[0046]FIG. 3 illustrates a block diagram of the AP in accordance withthe present invention.

[0047]FIG. 4 illustrates a block diagram of the PLB in accordance withthe present invention.

[0048]FIG. 5 illustrates a conceptual diagram of a power line couplingin accordance with one embodiment of the present invention.

[0049]FIG. 6 illustrates a diagram of a self-contained power linecoupling in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0050] Referring to FIG. 1, the typical electric distribution topologyof the prior art is illustrated. Medium voltage (MV) half loop powerdelivery system, as illustrated, is common to the U.S. PDS. Manytransformers are used. Each transformer services a few homes or smallbusinesses. Many other countries, such as the European states, use ahigh voltage delivery system with many end users serviced from atransformer. The present invention applies to either environment.

[0051] The present invention may be implemented in a high voltage andmedium voltage PDS environment. For purposes of this description andsubsequent claims, the high and medium voltage portion of the PDS isdescribed as “primary” voltage (PV). The low voltage portion of thesystem is described alternatively as LV or “secondary” voltage (SV).These terms are arbitrary but used to improve clarity of thedescription. Similarly, the side of a transfer where the PV line entersis called the “primary” side. The SV side of the transformer is referredto as the “secondary” side of the transformer.

[0052] A sub-station 10 delivers PV power to a half loop distributionpoint, pole dip 12. The power is delivered in parallel to multipletransformers 20 over a PV power line 14. After the transformer isstepped down to a SV power (in the range of 100 to 240 VAC), several enduser premises 26 are serviced via a SV power line 24. The step downtransformer 20 grounds high frequency signals for safety purposes. Sincea high data transfer (high bandwidth) power line communication deliverysystem requires a high frequency signal carrier, an object of thepresent invention is to avoid the removal of the high frequency signalby the transformer 20. It is noted that the PV power lines 14 may beabove ground or subterranean. The transformers 20 may be aerial mountedon a pole or pad mounted on the ground.

[0053] Referring to FIG. 2 the typical electric distribution topology asshown in FIG. 1 as modified for communication in accordance with thepresent invention is illustrated. A point of presence 40 (POP), theterminus for high frequency, high bandwidth data signal, serves as thegateway to the digital communications world. It both sends and receivesdata to the end user over the PDS. A backhaul link 42 connects the POP40. Data is manipulated and coupled and de-coupled from the PV powerline at an aggregation point 44 (AP). A more detailed description of theAP follows in the FIG. 3 discussion.

[0054] The PDS is viewed as having three channels: PV power line; SVpower line; and the premise's wiring. The first channel (the PV cable)has the least amount of noise and least amount of reflections. Thischannel has the highest potential bandwidth for communications. This isimportant because it is the channel that concentrates all of thebandwidth from the other channels. The type of signal used on thischannel can be almost any signal used in communications (CDMA, TDMA,FDM, OFDM to name a few). A wideband signal such as CDMA that isrelatively flat in the spectral domain is preferred to minimize radiatedinterference to other systems while delivering high data rates.

[0055] The second channel (SV line from the transformer to the premise)and third channel (premise wiring) have noise present from electricalappliances and reflections due to the “web” of wires. These channels cansupport a lower bandwidth than the PV channel and they need a moreintelligent (with more overhead) modulation schemes. There are severalcompanies with chip sets to achieve good communications for local areanetworks (LANs) such as: Adaptive Networks (Newton, Mass.), Inari(Draper, Utah), Intellion (Ocala, Fla.), DS2 (Valencia, Spain) and Itran(Beer-Sheva, Israel). These devices would work well for the SV andpremise channels.

[0056] Data signal and power are carried over the PV power line 14 aspreviously stated. A power line bridge 46 (PLB) allows the data signalto bypass the transformer 20 thus avoiding the grounding of the highfrequency data signal. More description of the PLB follows in the FIG. 4description. The data signal after manipulation is delivered to the enduser's premise. The data signal enters premise via the SV wiring. Theend user may have a local area network (LAN) or have individual digitalappliances.

[0057] In one embodiment of the present invention, the signal is carriedthrough the premise's wiring and is available to various digitalappliances 29, 30, including PC's, by a power line interface device 28(PLID). The PLID 28 plugs into a standard electrical socket and allowsthe digital appliance to send and receive digital data. An alternativeembodiment as described later, uses a communications interface locatedoutside of the premise and the data signal is directly fed to thepremise.

[0058] Referring next to FIG. 3, a block diagram of the AP in accordancewith the present invention is illustrated. The AP 44 is the point wheredigital data is coupled and de-coupled to the PV power line.Additionally, the data is processed so that it can be readilycommunicated. Data signal communication to and from POP 40 is providedby the backhaul link 42.

[0059] A backhaul interface 50 allows direct communication with POP 40.The signal is passed through a signal modem 52 (PV modem). An isolator54 is used to prevent electric current from flowing between the PDS andthe components leading to the POP 40. The isolator 54 is made fromdielectric material. The isolator, in a preferred embodiment of thepresent invention, is a fiber optic light pipe. More description of theisolator and its components occurs in the description referring to FIG.6.

[0060] The isolator 54 bridges between the PV modem 52 and a power linecoupler 56 (PLC). The PV modem 52 within the AP 44 conditions the signalfor transmission over the PV power line 14. When data is transmitted bythe end user and is de-coupled off of the PV power line, the PV modem 52conditions the signal for transmission back to the POP 40.

[0061] In one embodiment of the present invention the PLC 56 comprises,along with other components, an inductor having a toroid (donut-like)shaped core. The toroid core has permeability qualities to maximizesignal to noise ratio. More description of a preferred embodiment forthe PLC is presented below. The inductor component couples andde-couples a high frequency signal to and from the power line withoutinvading the power line. Once the data signal has been coupled to the PVpower line, it is transported on the PV power line 14.

[0062] Referring to FIG. 4, a block diagram of the PLB in accordancewith the present invention is illustrated. The PLB 46 bypasses thetransformer 20 linking the data signal between the PV power line and theSV power line. At either end of the PLB 46 is a coupler. A PV coupler 60couples and de-coupes signal with a PV power line 14. A SV coupler 72couples and de-coupes signal with a SV power line 24.

[0063] An isolator is present between the PLB end couplers 60,72 and theinterior of the PLB 46. The isolators, a PV isolator 62 and a SVisolator 70, are composed of dielectric material and insulate thebalance of the PLB from potential electrical damage and user injury. Apreferred embodiment of the isolator uses fiber optic material. Theisolator will be discussed in more detail below.

[0064] A PV modem 64 modulates and de-modulates the signal to and fromthe PV isolator. The PV modem conditions the high frequency signals fortransmission over the PV power line 14. The SV modem 68 conditions thesignal for communication over a SV power line. In one embodiment of thepresent invention, a data router 66 is between the SV modem 68 and thePV modem 64. The function of the data router 66 is to prioritize andgather packets from all of the devices on SV power line side PV powerline side. The data router 66 provides data packet management of enduser transmission.

[0065] The signal (going to the end user) is coupled onto the SV powerline by the SV coupler 72. The SV power line 24 delivers the powerservice to an end user premise 26. A “web” of wires distributes powerand signal within the premise. The user draws power on demand byplugging an appliance into a power outlet. In a similar manner, the usermay use a power line interface device 28 (PLID) to digitally connectdata appliances to receive and send data signals carried by the powerwiring.

[0066] A PLID 28 can have a variety of interfaces to the subscriber'sequipment 29, 30.

[0067] Some examples are RJ-11 Plain Old Telephone Service (POTS),RS-232, USB, and 10 Base-T. A subscriber can have multiple PLIDs 28 onthe same internal wiring.

[0068] Referring to FIG. 5, a conceptual diagram of a power linecoupling in accordance with one embodiment of the present invention isillustrated. The prior disclosed embodiments of the PLCS include a PLB46. The embodiment conceptualized in FIG. 5 replaces the PLB 46 with aself-contained power line coupler 100, a fiber optic isolator 130 and acommunications interface 140. Further, the transformer 20 is depicted aspole mounted. The Communications Interface 140 separates signal carriedover the PV power line 14 into three components: SV power line 24;wireless link 150; and telephone line 160.

[0069] Referring to FIG. 6, a diagram of a self-contained power linecoupling in accordance with one embodiment of the present invention isillustrated. The self-contained PLC is packaged in a weatherproofhousing 102 to militate against harsh weather and environmentconditions. The PV power line 14 passes through sealed openings in thecontainer. A data signal coupler 104 couples and de-couples data signalstransported by the PV power line 14. One embodiment of the presentinvention uses a magnetic toroid shaped inductor. Windings 108 areplaced around the inductor 104 to facilitate flux linkage of the datasignal. The number of windings and the winding orientation is selectedto maximize flux linkage. The permeability of the magnetic core ischosen for maximum coupling with the high frequency data signal. Thepermeability characteristics must also prevent low frequency (50-60 Hz)power line signal saturation of the toroid core to allow the data signalto couple and de-couple.

[0070] The toroid has direct electrical connection to the signalconditioning electronics used for transmitting and receiving the datasignal. Transmit and receive circuitry 110 carries data signal to signalconditioning electronic components. As depicted in FIG. 6, the transmitcircuitry 112 and the receive circuitry 114 are in parallel. Anotherembodiment of the present invention employs two data signal couplingtoroids as opposed to one data signaling coupling toroid as depicted.One coupler for receiving and one for transmitting in order to optimizethe flux linkage for the two cases.

[0071] The design of the transmit side is done to maximize the power ofthe drive signal in order to keep the signal to noise ratio of thecoupled signal at least to the level acceptable for the overallcommunications system. The receive side contains a low noise amplifierdesigned to handle the lowest acceptable transmit signal level of thesystem. At a system level, the modulation and signaling scheme is doneto minimize interference between transmit and receive signals.

[0072] The signal conditioning circuitry is connected to the fiberoptics interface via an electro-optical transducer 116, such as laserdiodes. The transducer converts an electrical signal to a light signalin the receive circuitry 114. The transducer converts light signals toelectrical signals in the transmit circuitry 112. The light signal istransmitted to and from a light pipe 130 to a fiber-optic isolator 120(fiber optic line or cable). The data signals are communicated back andforth between the PLC 100 and the Communications Interface 140 via afiber optic line 120. The Fiber Optic Isolator breaks any electricalpath between the two devices and provides the inherent safety requiredby the power distributors.

[0073] With the PLC being a “closed” system, power for the electronicsmust be derived internally. Although batteries may be an option,replacement would be costly and impractical. As a result, the PLCcontains a power draw toroid 106 having magnetic characteristicsappropriate for coupling 60 Hz signals that will inductively draw someof the 60 Hz signal off of the power line charging a power supply 118component. The power supply 118 powers the PLC electronics.

[0074] For additional safety, the PLC housing 102 is constructed withhigh dielectric, corrosive resistant materials and is designed tosignificantly reduce any possible exposure to the high voltage potentialpresent on the power line. The fiber optic isolator 120 and light pipe130 is the only connection between the PLC 100 and the communicationsinterface 140. Further, the light pipe 130 is encased in the insulatedhousing 102. The housing's 102 first priority is to protect exposure tothe high voltage potential. It is also designed to ensure properoperation under extreme environmental conditions.

[0075] In another embodiment of the present invention, a “hinged” toroiddesign allows for easy installation and minimal impact to customerservice. The toroid simply snaps around the power line using existingutility tools and techniques.

[0076] The communications interface 140 communicates with the PLC 100via the fiber optic isolator 120. Received signals are separated intodigital data signals and any other communication signal that may becarried by the PV power line. FIG. 5 depicts three types of leads fromthe communications interface: 120/240 V power line 24 (SV power line);wireless link 150; and telephone link 160. The SV power line receivescurrent from the transformer 24. The digital data signal is coupled onand off the SV power line 24 within the communications interface.

[0077] The description of one embodiment of the present invention forthe PLB 46 providing a means for converting light signals received via aPV isolator to coupled digital data signals as delivered to a premiseover SV power line has been offered above. The communications interfaceimplements the coupling and de-coupling of digital data signal on andoff the SV power line in a similar fashion.

[0078] A system as disclosed herein is useful to provide data servicesto the residential market place at 10 Mbps. This makes an entire newrange of applications practically available. Each device that isconnected to the power would (if desired) have an address and would beaccessible remotely. Some examples include remote utility meter reading,Internet Protocol (IP)-based stereo systems, IP-based video deliverysystems, and IP telephony, although these are not meant as limitations.

[0079] The present invention has been described in terms of preferredembodiments, however, it will be appreciated that various modificationsand improvements may be made to the described embodiments withoutdeparting from the scope of the invention.

I claim:
 1. A method of safely transporting high-frequency signals overpower transmission lines, comprising the steps of: coupling andde-coupling high-frequency electrical signals on a first powertransmission line; converting said high-frequency electrical signals tolight signals and light signals to said high-frequency electricalsignals with an electro-optical transducer for coupling and de-couplingsaid high-frequency electrical signals to and from a non-electricallyconductive but light conductive medium.
 2. The method of claim 1,further comprising performing said steps within a non-electricallyconductive enclosure.
 3. The method of claim 1, wherein said lightconductive medium is a fiber-optic isolator.
 4. The method of claim 3,wherein said fiber-optic isolator is a fiber-optic transmission line. 5.The method of claim 3, further comprising transmitting said lightsignals to and from an interface device for digital appliances.
 6. Themethod of claim 3, further comprising: transmitting said light signalsto and from a second electro-optical transducer to for coupling andde-coupling said high-frequency electrical signals to and from anopposite end of said fiber-optic isolator; and coupling and de-couplingsaid high-frequency electrical signals on a second power transmissionline; so as to form an electrically isolated power line bridge.
 7. Anapparatus for safely transporting high-frequency signals over powertransmission lines, comprising: coupler means for coupling andde-coupling high-frequency electrical signals on a first powertransmission line; an electro-optical transducer capable of convertingsaid high-frequency electrical signals to light signals and lightsignals to said high-frequency electrical signals; and anon-electrically conductive but light conductive medium adjacent saidtransducer for coupling and de-coupling said light signals.
 8. Theapparatus of claim 7, further comprising a non-electrically conductiveenclosure for at least said coupler means and said transducer.
 9. Theapparatus of claim 7, wherein said light conductive medium comprises afiber-optic isolator.
 10. The apparatus of claim 9, wherein saidfiber-optic isolator is a fiber-optic transmission line.
 11. Theapparatus of claim 9, further comprising an interface device for digitalappliances connected to an opposite end of said fiber-optic isolator.12. The apparatus of claim 9, further comprising: a secondelectro-optical transducer connected to an opposite end of saidfiber-optic isolator for coupling and de-coupling said high-frequencyelectrical signals and said light signals to and from an opposite end ofsaid fiber-optic isolator; and a second coupling means for coupling andde-coupling said high-frequency electrical signals on a second powertransmission line so as to form an electrically isolated power linebridge.